ZK60-1Nd镁合金的组织结构及腐蚀行为

Microstructure and Corrosion Behavior of ZK60-1Nd Magnesium Alloy

通过扫描电镜(SEM),X射线衍射仪(XRD),电化学工作站和盐水浸泡失重法研究了ZK60-1Nd镁合金的组织结构及在3.5%(质量分数)NaCl水溶液中的腐蚀行为。结果表明:ZK60-1Nd镁合金主要由基体α-Mg相,沿晶界分布的含有稀土元素Nd的粗大网状相组成。ZK60-1Nd镁合金在3.5%的NaCl水溶液中的腐蚀速率为0.2mg·cm^(-2)·h^(-1);经过400℃保温96h后,部分共晶相熔断成尺寸约为0.5μm的颗粒,腐蚀速率降低到0.1mg·cm^(-2)·h^(-1);经过500℃保温8.0h,网状共晶相熔化成分散块状,基体中细小棒状相溶解消失,Nd,Zn和Zr元素在基体中含量增加且分布均匀,腐蚀速率达到最低,为0.03mg·cm^(-2)·h^(-1)。其耐蚀性能改善的主要原因为α-Mg基体中固溶态Nd元素含量的增加导致合金自腐蚀电位提高以及基体α-Mg中腐蚀微电偶数目的减少。

Microstructure and corrosion behavior of ZK60-1Nd magnesium alloy in 3.5 wt% NaC1 aqueous solution were studied by scanning electron microscope （SEM）, X-ray diffractometer （XRD）, electrochemical workstation and a brine weight loss method. The results indicate that the as-cast microstructure of the ZK60-1Nd alloy is mainly composed of matrix a-Mg, and a coarse network eutectic MgZn2 phase containing rare earth Nd distributed along the grain boundaries. The corrosion rate of the alloy in 3.5 wt% NaC1 aqueous solution is 0.2 mg.cm-2.h-1. After annealing at 400℃ for 96 h, part of the eutectic phase is fused to particles with a maximum size of 0.5 μm and the corrosion rate is reduced to 0.1 mg·cm^-2·h-1. After annealing at 500 ℃ for 8.0 h, fishbone eutectic phase is fused to patchy, the MgZn2 phase is dissolved into the matrix, the contents of Nd, Zn and Zr are increased with uniform distribution in the matrix, and the corrosion rate reaches a minimum of 0.03 mg.cm2·h1. The improvement of corrosion resistance is attributed to the increase of the solid solution Nd content in matrix a-Mg, which increases the corrosion potential and decreases micro galvanic corrosion in number.